Abstract: A method and apparatus for obtaining seismic vibrator reflection data is disclosed with a significant signal to noise ratio. The earth is sinusoidally vibrated with source vibrations linearly varying over time. The amplitudes of the reflections from the subsurface strata interfaces are sensed and multiplied by the amplitude of the source vibrations, resulting in a first representation of the product as a function of time. A second representation of the product is calculated in association with negative values of time, such that phase consistency between the two representations is maintained. The two representations are then mathematically combined, with values of zero associated with all other values of time. The two representations are then linearly transformed into a function of frequency, and loaded into an array for computer operation.